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Spatiotemporal dynamics of triglyceride storage in unilocular adipocytes.

Chu M, Sampath H, Cahana DY, Kahl CA, Somwar R, Cornea A, Roberts CT, Varlamov O - Mol. Biol. Cell (2014)

Bottom Line: Exogenously added free fatty acids are rapidly adsorbed by mLDs and concurrently get esterified to TG.This process is greatly accelerated by insulin. mLDs transfer their content to the cLD, serving as intermediates that mediate packaging of newly synthesized TG in the large interior of a unilocular adipocyte.This study reveals novel cell biological features that may contribute to the mechanism of adipocyte hypertrophy.

View Article: PubMed Central - PubMed

Affiliation: Division of Endocrinology, Diabetes, and Clinical Nutrition, Department of Medicine, Portland, OR 97239.

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Electron microscopy of a unilocular adipocyte. A visceral WAT explant was fixed and processed for electron microscopy, as described in Materials and Methods. cLD, central LD; mLD, micro-LD; PM, plasma membrane, rER, rough ER; sER, smooth ER; M, mitochondria. (A) Low-magnification image of the cytoplasmic nodule, containing various organelles. mLDs are in close proximity to the cLD. (B, C) mLDs are associated with mitochondria and the sER. Contact sites between mLDs and mitochondria are marked with asterisks. (B–D) Arrowheads indicate vesicles budding off the ER tubules. (E) Example of a mLD adjacent to electron-lucent vesicular material, which may represent the precursors for mLDs and/or the cross sections of the ER tubules. (F) Area of the adipocyte cytoplasm enriched in the rER (decorated with polyribosomes) and the Golgi. Golgi membranes are surrounded by vesicles containing electron-dense cores. Bar, 500 nM.
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Figure 3: Electron microscopy of a unilocular adipocyte. A visceral WAT explant was fixed and processed for electron microscopy, as described in Materials and Methods. cLD, central LD; mLD, micro-LD; PM, plasma membrane, rER, rough ER; sER, smooth ER; M, mitochondria. (A) Low-magnification image of the cytoplasmic nodule, containing various organelles. mLDs are in close proximity to the cLD. (B, C) mLDs are associated with mitochondria and the sER. Contact sites between mLDs and mitochondria are marked with asterisks. (B–D) Arrowheads indicate vesicles budding off the ER tubules. (E) Example of a mLD adjacent to electron-lucent vesicular material, which may represent the precursors for mLDs and/or the cross sections of the ER tubules. (F) Area of the adipocyte cytoplasm enriched in the rER (decorated with polyribosomes) and the Golgi. Golgi membranes are surrounded by vesicles containing electron-dense cores. Bar, 500 nM.

Mentions: We further examined the ultrastructural organization of mLDs in unilocular adipocytes using electron microscopy. Electron-lucent mLDs ranging up to 1 μm in diameter were frequently observed in adipocyte cytoplasm in the vicinity of or attached to the cLD (Figure 3A). mLDs were surrounded by or associated with mitochondria (Figure 3, A–C). Tubular membranes of the smooth ER decorated with budding vesicles were frequently observed in the areas containing mLDs and mitochondria (Figure 3, B–D, arrowheads). Furthermore, some mLDs were decorated by electron-lucent vesicular material, which may represent the ER or precursors of mLDs (Figure 3E). Of interest, rough ER membranes were not typically associated with mLDs (Figure 3F).


Spatiotemporal dynamics of triglyceride storage in unilocular adipocytes.

Chu M, Sampath H, Cahana DY, Kahl CA, Somwar R, Cornea A, Roberts CT, Varlamov O - Mol. Biol. Cell (2014)

Electron microscopy of a unilocular adipocyte. A visceral WAT explant was fixed and processed for electron microscopy, as described in Materials and Methods. cLD, central LD; mLD, micro-LD; PM, plasma membrane, rER, rough ER; sER, smooth ER; M, mitochondria. (A) Low-magnification image of the cytoplasmic nodule, containing various organelles. mLDs are in close proximity to the cLD. (B, C) mLDs are associated with mitochondria and the sER. Contact sites between mLDs and mitochondria are marked with asterisks. (B–D) Arrowheads indicate vesicles budding off the ER tubules. (E) Example of a mLD adjacent to electron-lucent vesicular material, which may represent the precursors for mLDs and/or the cross sections of the ER tubules. (F) Area of the adipocyte cytoplasm enriched in the rER (decorated with polyribosomes) and the Golgi. Golgi membranes are surrounded by vesicles containing electron-dense cores. Bar, 500 nM.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Figure 3: Electron microscopy of a unilocular adipocyte. A visceral WAT explant was fixed and processed for electron microscopy, as described in Materials and Methods. cLD, central LD; mLD, micro-LD; PM, plasma membrane, rER, rough ER; sER, smooth ER; M, mitochondria. (A) Low-magnification image of the cytoplasmic nodule, containing various organelles. mLDs are in close proximity to the cLD. (B, C) mLDs are associated with mitochondria and the sER. Contact sites between mLDs and mitochondria are marked with asterisks. (B–D) Arrowheads indicate vesicles budding off the ER tubules. (E) Example of a mLD adjacent to electron-lucent vesicular material, which may represent the precursors for mLDs and/or the cross sections of the ER tubules. (F) Area of the adipocyte cytoplasm enriched in the rER (decorated with polyribosomes) and the Golgi. Golgi membranes are surrounded by vesicles containing electron-dense cores. Bar, 500 nM.
Mentions: We further examined the ultrastructural organization of mLDs in unilocular adipocytes using electron microscopy. Electron-lucent mLDs ranging up to 1 μm in diameter were frequently observed in adipocyte cytoplasm in the vicinity of or attached to the cLD (Figure 3A). mLDs were surrounded by or associated with mitochondria (Figure 3, A–C). Tubular membranes of the smooth ER decorated with budding vesicles were frequently observed in the areas containing mLDs and mitochondria (Figure 3, B–D, arrowheads). Furthermore, some mLDs were decorated by electron-lucent vesicular material, which may represent the ER or precursors of mLDs (Figure 3E). Of interest, rough ER membranes were not typically associated with mLDs (Figure 3F).

Bottom Line: Exogenously added free fatty acids are rapidly adsorbed by mLDs and concurrently get esterified to TG.This process is greatly accelerated by insulin. mLDs transfer their content to the cLD, serving as intermediates that mediate packaging of newly synthesized TG in the large interior of a unilocular adipocyte.This study reveals novel cell biological features that may contribute to the mechanism of adipocyte hypertrophy.

View Article: PubMed Central - PubMed

Affiliation: Division of Endocrinology, Diabetes, and Clinical Nutrition, Department of Medicine, Portland, OR 97239.

Show MeSH
Related in: MedlinePlus